by Grant Allen
In 1852, once more, so eminent and confirmed an evolutionist as Mr. Herbert Spencer himself had hit upon a glimpse of the same great truth, strange to say without perceiving the width and scope of its implications. ‘All mankind,’ he wrote in that year in an essay on population in the ‘Westminster Review,’ ‘in turn subject themselves more or less to the discipline described; they either may or may not advance under it; but, in the nature of things, only those who do advance under it eventually survive. For, necessarily, families and races whom this increasing difficulty of getting a living which excess of fertility entails does not stimulate to improvements in production.... are on the high road to extinction; and must ultimately be supplanted by those whom the pressure does so stimulate.... And here, indeed, without further illustration, it will be seen that premature death, under all its forms, and from all its causes, cannot fail to work in the same direction. For as those prematurely carried off must, in the average of cases, be those in whom the power of self-preservation is the least, it unavoidably follows that those left behind to continue the race must be those in whom the power of self-preservation is the greatest, must be the select of their generation.’ In this striking pre-Darwinian passage we have a partial perception of what Mr. Spencer afterwards described as the survival of the fittest; but, as our great philosopher himself remarks, it ‘shows how near one may be to a great generalisation without seeing it.’ For not only does Mr. Spencer, like Wells before him, limit the application of the principle to the case of humanity; but, unlike Wells, he overlooks the all-important factor of spontaneous variation, and the power of natural selection, acting upon such, to produce specific and generic divergences of structure. In short, in his own words, the paragraph ‘contains merely a passing recognition of the selective process, and indicates no suspicion of the enormous range of its effects, or of the conditions under which a large part of its effects are produced.’ On the other hand, it must be noted that both Spencer and Matthew, like Darwin himself, based their ideas largely upon the Malthusian principle, and thus held the two true keys of the situation fairly within their unconscious hands.
Frankly to recognise these various foreshadowings of the distinctive Darwinian theory of natural selection is not in any way to undermine the foundations of Charles Darwin’s own real and exceptional greatness. On the contrary, the mere fact that his views were so far anticipated by Wells, Matthew, Spencer, and others, and were simultaneously arrived at across half the globe by the independent intellect of Alfred Russel Wallace, is in itself the very best proof and finest criterion of Charles Darwin’s genuine apostleship. No truly grand and fruitful idea was ever yet the sole property of a single originator. Great discoveries, says an acute critic, must always be concerned with some problem of the time which many of the world’s foremost minds are just then cudgelling their active brains about. It was so with the discovery of the differential calculus, and of the planet Neptune; with the interpretation of the Egyptian hieroglyphics, and of the cuneiform inscriptions; with the undulatory theory of light, with the mechanical equivalent of heat, with the doctrine of the correlation and conservation of energies, with the invention of the steam engine, the locomotive, the telegraph and the telephone; with the nebular hypothesis, and with spectrum analysis. It was so, too, with the evolutionary movement. The fertile upturning of virgin sod in the biological field which produced Darwin’s forerunners, as regards the idea of descent with modification, in the persons of Buffon, Lamarck, and Erasmus Darwin, necessarily produced a little later, under the fresh impetus of the Malthusian conception, his forerunners or coadjutors, as regards the idea of natural selection, in the persons of Wells, Matthew, and Wallace. It was Darwin’s task to recognise the universal, where Wells and Spencer had seen only the particular; to build up a vast and irresistible inductive system, where Matthew and Wallace had but thrown out a pregnant hint of wonderful a priori interest and suggestiveness. It is one thing to draw out the idea of a campaign, another thing to carry it to a successful conclusion; one thing rudely to sketch a ground-plan, another thing finally to pile aloft to the sky the front of an august and imposing fabric.
As soon as the papers at the Linnean had been read and printed, Darwin set to work in real earnest to bring out the first instalment of his great work. That instalment was the ‘Origin of Species.’ The first edition was ready for the public on November the 24th, 1859.
In his own mind Darwin regarded that immortal work merely in the light of an abstract of his projected volumes. So immense were his collections and so voluminous his notes that the ‘Origin of Species’ itself seemed to him like a mere small portion of the contemplated publication. And indeed he did ultimately work out several other portions of his original plan in his detailed treatises on the Variation of Animals and Plants under Domestication, on the Effects of Cross and Self-Fertilisation, and on the Descent of Man and Sexual Selection. But the immense and unexpected vogue of his first volume, the almost immediate revolution which it caused in biological and general opinion, and the all but universal adhesion to his views of all the greatest and most rising naturalists, to a great extent saved him the trouble of carrying out in full the task he had originally contemplated as necessary. Younger and less occupied labourers took part of the work off their leader’s hands; the great chief was left to prosecute his special researches in some special lines, and was relieved from the necessity of further proving in minuter detail what he had already proved with sufficient cogency to convince all but the wilfully blind or the hopelessly stupid.
The extraordinary and unprecedented success of the ‘Origin of Species’ is the truest test of the advance it made upon all previous evolutionary theorising. Those who had never been convinced before were now convinced by sheer force of reasoning; those who believed and those who wavered had their faith confirmed into something like the reposeful calm of absolute certitude.
Let us consider, therefore, what exactly were the additions which Charles Darwin offered in his epoch-making work to the pre-existing conceptions of evolutionists.
In 1852, seven years before the publication of Darwin’s masterpiece, Mr. Herbert Spencer wrote as follows in an essay in the ‘Leader’ on creation and evolution. The expressions of so profound and philosophical a biologist may be regarded as the high-water mark of evolutionary thinking up to the date of the appearance of Wallace and Darwin’s theory: —
‘Even could the supporters of the development hypothesis merely show that the production of species by the process of modification is conceivable, they would be in a better position than their opponents. But they can do much more than this; they can show that the process of modification has effected and is effecting great changes in all organisms, subject to modifying influences ... they can show that any existing species — animal or vegetable — when placed under conditions different from its previous ones, immediately begins to undergo certain changes of structure fitting it for the new conditions. They can show that in successive generations these changes continue until ultimately the new conditions become the natural ones. They can show that in cultivated plants and domesticated animals, and in the several races of men, these changes have uniformly taken place. They can show that the degrees of difference, so produced, are often, as in dogs, greater than those on which distinctions of species are in other cases founded. They can show that it is a matter of dispute whether some of these modified forms are varieties or modified species. They can show too that the changes daily taking place in ourselves; the facility that attends long practice, and the loss of aptitude that begins when practice ceases; the development of every faculty, bodily, moral or intellectual, according to the use made of it, are all explicable on this same principle. And thus they can show that throughout all organic nature there is at work a modifying influence of the kind they assign as the cause of these specific differences, an influence which, though slow in its action, does in time, if the circumstances demand it, produce marked changes; an influence which, to all appearance, w
ould produce in the millions of years, and under the great varieties of condition which geological records imply, any amount of change.’
This admirable passage, written seven years before the publication of the ‘Origin of Species,’ contains explicitly almost every idea that ordinary people, not specially biological in their interests, now associate with the name of Darwin. That is to say, it contains, in a very philosophical and abstract form, the theory of ‘descent with modification’ without the distinctive Darwinian adjunct of ‘natural selection’ or ‘survival of the fittest.’ Yet it was just that particular lever, dexterously applied, and carefully weighted with the whole weight of his endlessly accumulated inductive instances, that finally enabled our modern Archimedes in so short a time to move the world. The public, that was deaf to the high philosophy of Herbert Spencer, listened at once to the practical wisdom of Charles Darwin. They did not care at all for the a priori proof, but they believed forthwith as soon as a cautious and careful investigator laid bare before their eyes in minute detail the modus operandi of nature herself.
The main argument of Darwin’s chief work runs somewhat after the following fashion: —
Variation, to a greater or less degree, is a common and well-known fact in nature. More especially, animals and plants under domestication tend to vary from one another far more than do the individuals of any one species in the wild state. Rabbits in a warren are all alike in shape, size, colour, and features: rabbits in a hutch vary indefinitely in the hue of their fur, the length of their ears, the character of their coat, and half a dozen other minor particulars, well known to the observant souls of boys and fanciers. This great variability, though partly perhaps referable to excess of food, is probably due on the whole to their having been raised under conditions of life not so uniform as, and somewhat different from, those to which the parent species is commonly exposed in a state of nature. In other words, variability is one result of altered and more varied surrounding circumstances.
Again, this variability is usually indefinite. You cannot say what direction it will take, or to what particular results it is likely in any special instance to lead. Marked differences sometimes occur even between the young of the same litter, or between the seedlings sown from the same capsule. As a rule, the variations exhibit themselves in connection with sexual reproduction; but sometimes, as in the case of ‘sporting plants,’ a new bud suddenly produces leaves or flowers of a different character from the rest of those on the self-same stem, thus showing that the tendency to vary is inherent, as it were, in the organism itself. Upon this fundamental fact of the existence in nature of numerous and indefinite variations, the whole theory of natural selection is ultimately built up. In illustrating by example the immense variability of domesticated creatures, Darwin lays great stress upon the case of pigeons, with which he was familiar from his long experience as a breeder and fancier in his own home at Down. Naturalists are almost universally of opinion that all the breeds of domestic pigeons, from the carrier to the tumbler, from the runt to the fantail, are alike descended from the wild rock pigeon of the European coasts. The immense amount of variation which this original species has undergone in domestication may be seen by comparing the numberless breeds of pigeon now exhibited at all our poultry shows with one another.
But variation gives us only half the elements of the ultimate problem, even in the case of domestic kinds. For the other half, we must have recourse to human selection, which, by picking out for seed or breeding purposes certain specially favoured varieties, has produced at last all the purposive or intentional diversity between the different existing stocks or breeds. In these artificially produced domestic races we see everywhere special adaptations to man’s particular use or fancy. The dray-horse has been fashioned for purposes of strength and sure-footedness in draught, the race-horse for purposes of fleetness in running. In the fox-hound, man has encouraged the special properties that tend to produce a good day’s hunting; in the sheepdog, those that make for the better maintenance and safety of a herd. The cauliflower is a cabbage, with specialised and somewhat abortive flower-heads; the fuller’s teasel is a sport of the wild form, with curved hooks specially adapted by a freak of nature for the teasing of wool. So in every case man, by deliberately picking out for breeding or seeding purposes the accidental variations which happened best to suit his own needs, has succeeded at last in producing races admirably fitted in the minutest particulars for the special functions to which they are applied. There appears indeed to be hardly any limit to the almost infinite plasticity and modifiability of domestic animals. ‘It would seem,’ said a great sheep-breeder, speaking of sheep, ‘as if farmers had chalked out upon a wall a form perfect in itself, and then proceeded to give it existence.’
Now, what is thus true within narrow limits, and in a short space of time about the deliberate action of man, Darwin showed to be also true within wider limits and spread over longer geological epochs about the unconscious action of nature. And herein consisted his great advance upon the earlier evolutionism of Lamarck, Goethe, and Erasmus Darwin. For while these instinctive pioneers of the evolutionary spirit saw clearly that animals and plants betrayed signs of common descent from one or a few original ancestors, they did not see what was the mechanism by which such organisms had been differentiated into so many distinct genera and species. They caught, indeed, at the analogy of variation under domestication and in the wild state, but they missed the subtler and deeper analogy between human and natural selection. Now, variation alone would give us a world consisting not of definite kinds fairly well demarcated one from the other, but of innumerable unclassified and unorganisable individuals, all shading off indefinitely one into the other, and incapable of being reduced by human ingenuity to any orderly hierarchical system. Furthermore, it would give us creatures without special adaptation of any kind to the peculiar circumstances of their own environment. To account for adaptation, for the almost perfect fitness of every plant and every animal to its position in life, for the existence (in other words) of definitely correlated parts and organs, we must call in the aid of survival of the fittest. Without that potent selective agent, our conception of the becoming of life is a mere chaos; order and organisation are utterly inexplicable save by the brilliant illuminating ray of the Darwinian principle. That is why Darwin destroyed at one blow the specious arguments of the early teleologists; he showed that where Chambers and even Erasmus Darwin had seen the working of a final cause, we ought rather to recognise the working of an efficient cause, whose outcome necessarily but fallaciously simulates the supposed features of an a priori finality.
From art, then, Darwin harks back once more to nature. He proceeds to show that variability occurs among all wild plants and animals, though not so frequently under ordinary circumstances as in the case of domesticated species. Individual differences everywhere occur between plant and plant, between animal and animal. Sometimes these differences are so very numerous that it is impossible to divide the individuals at all into well-marked kinds; for example, among British wild-roses, brambles, hawkweeds and epilobes, with a few other very variable families, Babington makes as many as 251 distinct species, where Bentham gives only 112 — a margin of 139 doubtful forms of shadowy indefiniteness. Varieties, in fact, are always arising, and dominant species in particular always tend to vary most in every direction. The reason why variation is not so marked in the wild state as under domestication is of course because the conditions are there less diverse; but where the conditions of wild things are most diverse, as in the case of dominant kinds, which range over a wide space of country or of ocean, abundant individual variations habitually occur. Local varieties thus produced are regarded by Darwin as incipient species: they are the raw material on which natural selection gradually exerts itself in the struggle for existence.
Granting individual variability, then, how do species arise in nature? And how are all the exquisite adaptations of part to whole, and of whole to environment, gradually i
nitiated, improved, and perfected?
Here Malthus and the struggle for life come in to help us.
For the world is perpetually over-populated. It is not, as many good people fearfully imagine, on a half-comprehension of the Malthusian principle, shortly going to be over-populated; it is now, it has always been, and it will always be, pressed close up to the utmost possible limit of population. Reproduction is everywhere and in all species for ever outrunning means of subsistence; and starvation or competition is for ever keeping down the number of the offspring to the level of the average or normal supply of raw material. A single red campion produces in a year three thousand seeds; but there are not this year three thousand times as many red campions as there were last summer, nor will there be three thousand times as many more in the succeeding season. The roe of a cod contains sometimes nearly ten million eggs; but supposing each of these produced a young fish which arrived at maturity, the whole sea would immediately become a solid mass of closely packed codfish. Linnæus reckoned that if an annual plant had two seeds, each of which produced two seedlings in the succeeding season, and so on continually, in twenty years their progeny would amount to a million plants. A struggle for existence necessarily results from this universal tendency of animals and plants to increase faster than the means of subsistence, whether those means be food, as in the first case, or carbonic acid, water, and sunshine as in the second. Animals are all perpetually battling with one another for the food-supply of the moment; plants are perpetually battling with one another for their share of the soil, the rainfall, and the sunshine.
